1. Field of the Invention
The present invention relates to a vented gas riser apparatus. More specifically, it relates to a vented gas riser apparatus which includes a buried containment chamber in combination with a vent passageway to allow for gas which leaks into the containment chamber to be directed into the atmosphere in at an above ground location.
2. Description of the Prior Art
A variety of prior art patents for various natural gas meter riser systems are known in the industry. For example, the following patents each describe various configurations of natural gas risers:
Godkin, U.S. Pat. No. 4,284,297 discloses a meter riser where the upper end of the plastic tubing and metal pipe casing are adjacent and structurally secured to each other in a sealed fashion by a plastic transition adapter and a cooperating metal fitting. In column 4 lines 63 through 65 a gas seal for preventing leakage of the fluid flowing from the gas main to the gas meter is provided between the adapter 20 and fitting 40 by the compressed O-rings 26.
Lorenz et al, U.S. Pat. No. 5,326,137 discloses a gas riser comprising a pipe nipple, casing, adaptor sleeve, tube and stiffener. In FIG. 2 and described in column 4 lines 14 through 22 first and second seal members 50, 52 are typically disposed between the inner tube and outer casing of the double walled riser. The first or upper seal member 50 limits the flow of the fluid between the tube 40 and the outer casing 30. Moreover, the second seal member 52 is often times used to prevent water and dirt from entering the annular space between the tube and casing at an area disposed underground.
Platner et al, U.S. Pat. No. 5,590,914 discloses a gas riser including an adapter having plural inner grooves. Axial advancement of a stiffener acts as a mandrel to physically deform the gas line into the grooves and provide a secure, sealed arrangement. As taught in column 3 lines 12 and 13, a pair of spacers 50, 52 provide a sealed arrangement between the inner and outer conduits 30, 40.
Robinson et al, U.S. Pat. No. 7,125,052 discloses a riser assembly which includes a seal assembly interposed between the inner casing and the adapter for sealing therebetween. A gripping assembly holds the inner casing in the adapter. The seal assembly is described in column 6 lines 13 through 27 and is defined by a first and second seal member 104, 106 interposed between the conduit 22 and the adapter 30 for sealing therebetween. Seals 104, 106 prevent the passage of fluid there past in either axial direction between the outer surface of the conduit 22 and the adapter 30. Additional details are given.
Jacobson et al, U.S. Pat. No. 4,482,170 discloses a gas riser which includes annular resilient seal which frictionally engages the exterior of the conduit abutting the annular collar. The resilient seal engages the tapered portion, and the annular collar pressing into engagement with the tapered portion and compressing the resilient seal against the retaining ring, the O.D. of the conduit and the I.D. of the iron pipe. Described in column 3 line 61 through 63 the tapered portion 66 is frictionally engaged by the resilient seal 36 to provide a gas impermeable seal there between. A ground water sealing means 58 includes a resilient gasket 80 is described in column 4 line 7 through 10.
Gady, U.S. Pat. No. 5,934,711 discloses a mold shot riser element with O-ring sealing which allegedly provides improved sealing between an inner pipe and an outer pipe of the riser apparatus. Referring to column 3 lines 35 to 39 the sealing elements 12 include a plurality of O-rings 30 and a cylindrical sealing gasket 32. The sleeves 24, 26, 28 define locating means for the O-rings 30 and gasket 32 which serves to capture the sealing elements and retain them in place. Gady also teaches at column 4 lines 27 through 35 that a seal 60 which is schematically illustrated in FIG. 5 limits the flow of fluid between the inner and outer pipes such that an annular space 62 between the inner and outer pipes below the seal 60 is not filled with pressurized gas. Only the limited annular space 64 above the seal 60 is filled with the pressurized gas. The seal 60 is preferably located above ground level. Thus, the outer pipe 14 acts as a carrier of fluid only for a small portion if its length above ground level and above the seal. Other details are provided at line 36 through 50.
Alewitz, U.S. Pat. No. 4,279,435 discloses a gas riser apparatus which includes gasket seals 140 and 142. As described in column 3 lines 43 to 47, in the preferred embodiment of FIG. 9, ribs 144 and 146 extend a degree sufficient to indent or displace material of the gasket seals 140, 142 in order to provide for sealing. Rib 148 similarly provides for sealing and locking of the members 112 and 134.
Wartluft, U.S. Pat. No. 5,366,260 and Wartluft et al., U.S. Pat. No. 5,692,785 disclose two known forms of plastic pipe couplers.
A common characteristic and feature of most, if not all, known gas riser systems is the provision of a riser casing which is sealed at an above ground location to some type of riser transition head (to which a meter is generally attached) so as to prevent any natural gas from escaping the system at the surface level. Historically, it has been considered to be a safety feature to provide a system which essentially provides a backup containment system at the surface so that in the unlikely event of a small gas leak at the meter connection, such leak would be captured between the gas carrier pipe and the protective riser casing and would likely seep into the earth at a location more distant from the building at which the meter is located.
An inherent problem with such a system, however, is that once gas leaks into the ground, because of a variety of geological formations which are not known and which are not predictable, it is difficult to predict where and how the natural gas will migrate. It is possible, that natural gas because of earth disturbances or other geological conditions will migrate and pool into a location underneath or near the building or structure thus leading to the possibility of a catastrophic explosion which would destroy the building.
It is important to bear in mind that these systems are designed so that the connection from a gas supply line source to a gas carrier pipe which leads to a delivery point at the meter location are designed not to leak at all and in most cases do not in fact leak. Thus, the present invention is directed only to a very small class of circumstances where a leak might occur. Such a leak could likely occur at one of two possible locations. The first location would be the point of connection between the gas supply source line and the gas carrier pipe of the riser and a second location would be the connection between the gas carrier pipe of the riser and the delivery point at the meter. In both of these cases, the type of leak might be either a fast and uncontrollable failure or might be a very slow seeping type leak. The present invention is directed only to situations where a slow seeping type leak might occur. While the concept of the present invention could possibly reduce the chances of an explosion in the event of a more rapid leak, the present invention is not designed for such circumstance and would be unlikely to provide adequate protection in such instances.
Contrary to the teachings of the prior art, the present invention teaches that rather than trying to either contain the leaked natural gas in a secondary containment casing system or to direct such leaks away from the gas riser down into the ground, that it is preferable to direct the leak to occur through a vent provided at a known location above ground near the meter. This would allow for the slow leak to be more likely to be detected and would allow the gas to be dispersed into the atmosphere thus reducing the chance of a catastrophic failure.